As of right now it will only run in MAME with the debug option on. Until it's recognized as a legitimate revision it won't pass the checksum it's expecting to see since it's modified from the original 3.1L. Once the project is complete I will submit a request for it to be included in the Database. Just add the option -debug MK2 to MAME to execute and don't forget F5 to start it once the debugger is shown.